Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. A typical knee prosthesis includes a tibial tray, a femoral component, and a polymer insert or bearing positioned between the tibial tray and the femoral component. In some cases, the knee prosthesis may also include a prosthetic patella component, which is secured to a posterior side of the patient's surgically-prepared patella. To prepare the patella, an orthopaedic surgeon first resects the posterior dome side of the patient's natural patella to secure the prosthetic component thereto. In use, the patella component articulates with the patient's natural or prosthetic femur during extension and flexion of the patient's knee.
To facilitate the replacement of the natural joint with the knee prosthesis, orthopaedic surgeons use a variety of orthopaedic surgical instruments such as, for example, cutting blocks, drill guides, milling guides, and other surgical instruments. Typically, the orthopaedic surgical instruments are generic with respect to the patient such that the same orthopaedic surgical instrument may be used on a number of different patients during similar orthopaedic surgical procedures.
In resecting the patella, surgeons frequently perform the resection free-hand. However, free-hand cutting the patella is not as accurate as a guided resection. Moreover, it is important that a sufficient amount of bone stock remain after resection to accept the fixation means for the patellar prosthesis and to maintain the integrity of the remaining patella. To ensure that the patella implant is properly positioned and that an appropriate amount of bone remains after resection, a resection guide is needed.
Depending on a number of factors, including the size of the patient, native patellae are of substantially different sizes. Accordingly, if a resection guide is to be used, either the guide must be provided in a plurality of sizes to accommodate variations in patellae size or an adjustable resection guide must be used.